A conventional brake control device for a vehicle is described at pages 118-119 of the publication entitled "Automotive Industry" published by Kelsey-Hayes Co. in Sep., 1996. This conventional brake control device for a vehicle includes a normally closed type valve which is disposed between a master cylinder and a wheel cylinder, and an accumulator that is connected to the front wheel cylinders through an electric regulator and an auxiliary pressure generator. The electric regulator detects the amount of operation of the brake pedal and regulates the fluid pressure in the accumulator according to the detected amount of brake pedal operation.
The auxiliary pressure generator includes a piston that is slidably disposed in a cylinder. The cylinder is divided in a fluid-tight manner into a first pressure chamber connected to the regulator and a second pressure chamber connected to the wheel cylinder. A spring is disposed in the second pressure chamber and urges the piston in a manner that reduces the volume of the first pressure chamber. The piston slides in the cylinder to reduce the volume of the second pressure chamber by the regulated fluid pressure flowing into the first pressure chamber from the regulator. Therefore, the fluid pressure in the wheel cylinder is increased to apply a brake force to the wheel.
The accumulator includes a hollow case divided by a dividing member into a high pressure gas chamber and a fluid pressure chamber. In the accumulator used in the conventional vehicle brake control device, gas that is mixed in the brake fluid in the fluid pressure chamber (which is leaked from the high pressure gas chamber through the dividing member) is prevented from being mixed in the brake fluid in the wheel cylinder to thereby secure the application of the brake force to the wheel because the wheel cylinder is fluid-tightly cut off from the accumulator by the auxiliary pressure generator.
The conventional vehicle brake control device described above suffers from certain disadvantages and drawbacks. For example, because the conventional brake control device includes the auxiliary pressure generator disposed between the accumulator and the wheel cylinder, a large number of parts are required to form the vehicle brake control device. This undesirably increases the cost of the brake control device.
In light of the forgoing, a need exists for a vehicle brake control device that is able to prevent the gas in the accumulator from being mixed in the brake fluid in the wheel cylinder through a regulator.
A need also exists for a vehicle brake control device that is able to address the foregoing while at the same time being relatively low in cost.